System in which a phased array antenna emulates lower directivity antennas

Abstract

A system includes a phased array antenna that is used to emulate antennas that have larger solid angle coverage and lower gain compared to a single beam of the phased array antenna. This is achieved by switching between beams of the phased array antenna while receiving a wireless communication signal and summing representations of signal energy received using the different beams. The system can be used to narrow down the angular coordinates of a transmitting satellite by emulating antenna patterns that cover portions of a search space. The system can also be used to determine a channel discriminator (e.g., frequency, code, time slot) that defines a signal being transmitted.

We claim: 
     
       1. A wireless receiver comprising:
 an antenna array; 
 a demodulator coupled to the antenna array; 
 a summer coupled to demodulator; and 
 a controller that controls the antenna array and the summer, and causes the antenna array to point in at least a first direction and a second direction different from the first direction while causing the summer to sum a first indication of signal strength produced by the demodulator when the antenna array is pointed in the first direction and a second indication of signal strength produced by the demodulator when the antenna array is pointed in the second direction, wherein the controller is programmed to establish the first direction during a first period within the duration of the code sequence and the second direction during a second period within the duration of the code sequence. 
 
     
     
       2. A method of receiving a radio signal, the method comprising:
 (a) receiving on an antenna array the radio signal comprising summing energy received on the antenna array during at least a first period and a second period; 
 (b) identifying in a demodulator a signal indicative of a duration of a code sequence in the radio signal received on the antenna array in said step (a); 
 (c) switching in a controller a beam of the antenna array in a first direction during the first period within the duration of the code sequence identified in the demodulator by said step (b); and 
 (d) switching in a controller the beam of the antenna array in a second direction different from the first direction during the second period within the duration of the code sequence identified in the demodulator of said step (b). 
 
     
     
       3. The method according to  claim 2  wherein the step (b) of identifying in the demodulator detects timing of the code sequence in part of a broadcast control channel or a satellite beacon. 
     
     
       4. The method according to  claim 2  wherein the step (b) of identifying in the demodulator identifies the code sequence is within a single data frame. 
     
     
       5. The method according to  claim 2 
 wherein the method further comprises (e) switching in the controller the beam of the antenna array in a third direction different from the first direction and the second direction during a third period within the duration of the code sequence, wherein the second period is between the first period and the third period identified in the demodulator of said step (b), and 
 wherein a total duration of time occupied by the first period, the second period and the third period is less than 20 milliseconds. 
 
     
     
       6. The method according to  claim 2  wherein step (b) of identifying in the demodulator accommodates both the first period and the second period within the duration of a single symbol of the code sequence. 
     
     
       7. A method of narrowing down a direction to a transmitting device, the method comprising:
 (a) receiving on an antenna array a radio signal comprising summing energy received on the antenna array; 
 (b) switching in a controller a beam of the antenna array in multiple directions within a solid angle portion of a larger solid angle search space during the receiving on the antenna array of said step (a), and 
 wherein said step (a) of summing energy received in the receiving of said step (a) occurs while switching by the controller the beam of the phased array antenna in the multiple directions of said step (b) comprises the substep (a)(1) by the controller of obtaining a summed received energy signal; and 
 (c) comparing in a comparitor of the controller the summed received energy signal from the antenna array obtained in said substep (a)(1) against a threshold to determine if the transmitting device is within the solid angle portion.